Apple Pay is the leader in contactless payments in the US, according to CEO Tim Cook.

Cook touted the performance of the Apple Pay service on Tuesday during a conference call to discuss the company's financial results last quarter. Though Apple continues to grapple with lower iPhone and iPad sales, Apple Pay is one area that's growing, both in the US and abroad.

Apple's CEO said that 3 million retail locations in the US now accept Apple Pay, which lets you make a purchase by simply waving your phone near certain point-of-sale registers -- hence the term "contactless."

Launched in 2014, Apple Pay lets you use an iPhone 6 or higher or an Apple Watch to pay for items on the go at supported merchants. For folks with Android phones, the alternatives include Samsung Pay and Google's Android Pay. Those services are all part of a larger movement -- factor in similar offerings from the likes of Walmart -- to make buying goods with a phone as second-nature as taking selfies.

Cook didn't reveal how many people tap into Apple Pay but said the number of estimated monthly active users last month rose more than 450 percent year over year. In April, the company said that Apple Pay picks up a million new users each week and accounts for more than five times the transaction volume from a year ago, according to a Seeking Alpha transcript.

Apple Pay is currently available in the US, the UK, Switzerland, Canada, Australia, China, France, Hong Kong and Singapore. But Apple has faced issues growing abroad. Banks in countries such as Canada and China have balked at the high transaction fees that Apple has stipulated, causing negotiations to drag on longer than anticipated.